This relates generally to electronic devices, and more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user.
Liquid crystal displays contain a layer of liquid crystal material. Pixels in a liquid crystal display contain thin-film transistors and pixel electrodes for applying electric fields to the liquid crystal material. The strength of the electric field in a pixel controls the polarization state of the liquid crystal material and thereby adjusts the brightness of the pixel.
There is a potential for ions in a liquid crystal display to move in response to applied electric fields. This can lead to charge accumulation on the pixels. Another cause of charge accumulation is dielectric polarization. Charge accumulation effects can produce visible artifacts on a display such as undesired flickering.
To minimize charge accumulation in a liquid crystal display the polarity of the electric field applied to the pixels may be periodically reversed. For example, alternating positive polarity and negative polarity frames of image data may be displayed on the pixels of a liquid crystal display to prevent excess positive or negative charge accumulation. Although periodic polarity reversal can help reduce charge accumulation, charge accumulation issues may still arise in liquid crystal displays. Charge accumulation may arise, for example, in situations in which a software application or other content generator creates negative and positive frames of image data with unbalanced gray levels. The risk of undesired charge accumulation may be exacerbated in displays with a variable refresh rate.
It would therefore be desirable to be able to provide displays with enhanced charge accumulation mitigation capabilities.